Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $44.42   8.706%   $48.2872   $48.29   $48.30   $48.30  
  Purchase #2 $173.79   13.735%   $197.6601   $197.66   $197.65   $197.70  
  Purchase #3 $78.32   11.232%   $87.1169   $87.12   $87.10   $87.10  
  Purchase #4 $133.34   10.453%   $147.278   $147.28   $147.30   $147.30  
  Purchase #5 $186.34   8.257%   $201.7261   $201.73   $201.75   $201.70  
  Purchase #6 $241.43   8.808%   $262.6952   $262.70   $262.70   $262.70  
  Purchase #7 $230.72   3.504%   $238.8044   $238.80   $238.80   $238.80  
  7 purchase totals = $1,088.36       $1,183.5679   $1,183.58   $1,183.60   $1,183.60